Switching converters are widely used in various electronic devices for sourcing power to the electronic devices from a power source. The electronic device(s) powered by a switching converter may be referred to as a load of the switching converter. Generally, the switching converter may be able to convert a power source voltage into an appropriate output voltage through controlling a switch module coupled to the power source voltage to switch on and off, thereby regulating power transmitted to the load.
The switching converter generally comprises a control module for controlling the switch module. The control module and the switch module in most switching converters are integrated and encapsulated in one package, and are referenced to an internal reference ground, which is usually connected to a ground pin of the package via a resistive connecting component. During the switch module switching on and off periodically, a relatively large switching current (compared with currents flowing through other internal circuits of the switching converter) may flow through the resistive component, resulting in an offset voltage from the reference ground to the package ground pin. Due to this offset voltage, the load regulation performance of the switching converter deteriorates. Load regulation of the switching converter may refer to change of the output voltage with an output current drawn by a load of the switching converter. It is an important criterion indicating the stability of the switching converter.
Typically, the control module of the switching converter regulates the output voltage by controlling the on and off switching of the switch module based on comparison of a feedback signal indicative of the output voltage with a reference signal indicative of a desired value of the output voltage, so as to achieve good load regulation. However, the reference signal is generally provided by a reference generation module integrated and encapsulated in the same package with the switch module and the control module. Therefore, the reference generation module is also referenced to the internal reference ground, and the reference signal provided bears the offset voltage with respect to the ground pin. When the load of the switching converter changes, the output current and the switching current also change, leading to variation in the offset voltage. The reference signal in consequence varies when referenced to the ground pin, which adversely worsen the load regulation.
A need therefore exists for solving the problem of influence of the offset voltage to the reference signal and the load regulation of a switching converter.